"Does Tea Tree Oil Have Hormonal Side Effects?"
Concern has been raised about a possible link between gynecomastia,
topical lavender, and tea tree oils.
Gynecomastia is the abnormal development of breast tissue.
I talked about lavender before, but what about tea tree oil?
It all started with a case series published in the New England Journal of Medicine.
They describe three young boys in whom breast growth coincided
with the topical application
of products that contained lavender and tea tree oils.
How do we know they were to blame?
Well, the problem resolved in each patient shortly after
the use of products containing these oils was stopped.
Furthermore, studies in human cell lines indicated that the two oils
had pro-female hormone and anti-male hormone activities.
So they conclude that repeated topical exposure
to lavender and tea tree oils probably was the cause.
But as a tea tree oil company representative pointed out,
only one of the three boys was exposed to any amount of tea tree oil,
and that subject was also exposed to lavender oil,
so lavender oil may have been to blame in all three cases.
The researchers responded that, OK, that's a valid argument,
however, the tea tree oil did have activity similar to that of lavender oil
with respect to the in vitro effects.
Let me walk you through those.
This is measuring the growth of human breast cancer cells in a petri dish.
You drip a tiny amount of estrogen on them,
and you can spike their growth, more than a dozen-fold.
But if you add an estrogen blocker along with the estrogen,
it abolishes the effect.
OK. Now, let's add increasing amounts of tea tree oil
to the breast cancer cells.
Their growth goes up, and the reason we know it's an estrogenic effect
is that when you add the estrogen blocker too,
the growth comes down.
Pretty convincing, but in vitro testing alone is not adequate grounds for
indicting traditionally used products, argued some herbal proponents—
including Paula Gardiner, I was excited to see,
one of my medical school classmates and friends. Hi, Paula!
Specifically, argued the Tea Tree Oil Industry Association,
only a few tea tree oil compounds actually make it through the skin,
so what they should have done is just measure the hormonal effects
of those three compounds.
But that had never been done until later that year.
Yes, drip increasing concentrations of whole tea tree oil on breast cancer cells
in a petri dish, and you can increase their growth,
compared to an oil with no estrogenic effect like eucalyptus oil.
But if you just look at the three components of tea tree oil
that actually make it into your bloodstream when you apply it
on your skin, none appear to have any estrogenic effects,
so none of the components that penetrate the skin
appears to act as estrogens, neither alone or in combination.
And so you can't extrapolate the petri dish effects of the whole oil
to what one might see when applied on the skin.
Thus what you see in a petri dish may not be identical to what you see in a person.
These new data led European consumer safety officials to conclude
that the purported link between gynecomastia
and the topical use of tea tree oil is therefore considered implausible.
In fact, if the anti-male hormone components of tea tree oil
remain on the skin, well, then, how about using it to treat women
who feel they are affected by excessive hairiness?
Such women were instructed to spray themselves
with a dilute lavender/tea tree oil spray versus placebo twice a day
on "problem" areas morning and evening for three months.
Hairs were taken before and after from four different body areas:
chin, chest, thigh, and upper arms.
After three months, no change in the hair diameter
in the placebo group, as expected,
but in the lavender/tea tree oil group, all the hairs ended up thinner.
This showed that at least the combination of lavender and tea tree oils
applied locally on the skin could be effective
in reducing mild excessive hairiness,
potentially representing a safe, economic, and practical
instrument in the cure of this "disease."